U.S. patent application number 13/455453 was filed with the patent office on 2012-08-16 for device with post-contact back end of line through-hole via integration.
Invention is credited to John Boyd, Yezdi Dordi, Shijian Li, Fritz Redeker, Hyungsuk Alexander Yoon.
Application Number | 20120205807 13/455453 |
Document ID | / |
Family ID | 40135635 |
Filed Date | 2012-08-16 |
United States Patent
Application |
20120205807 |
Kind Code |
A1 |
Boyd; John ; et al. |
August 16, 2012 |
DEVICE WITH POST-CONTACT BACK END OF LINE THROUGH-HOLE VIA
INTEGRATION
Abstract
Presented are device structures and methods of fabricating
three-dimensional integrated circuits that include post-contact
back end of line through-hole via integration for the
three-dimensional integrated circuits. Another aspect of the
present invention includes three-dimensional integrated circuits
fabricated according to methods of the present invention.
Inventors: |
Boyd; John; (Woodlawn,
CA) ; Redeker; Fritz; (Fremont, CA) ; Dordi;
Yezdi; (Palo Alto, CA) ; Yoon; Hyungsuk
Alexander; (San Jose, CA) ; Li; Shijian; (San
Jose, CA) |
Family ID: |
40135635 |
Appl. No.: |
13/455453 |
Filed: |
April 25, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12613518 |
Nov 5, 2009 |
8187968 |
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13455453 |
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11820811 |
Jun 20, 2007 |
7615480 |
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12613518 |
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Current U.S.
Class: |
257/751 ;
257/E23.011 |
Current CPC
Class: |
H01L 23/48 20130101;
H01L 2924/14 20130101; H01L 21/4763 20130101; H01L 21/76898
20130101 |
Class at
Publication: |
257/751 ;
257/E23.011 |
International
Class: |
H01L 23/48 20060101
H01L023/48 |
Claims
1. A microelectronic device comprising: at least one substrate
having semiconductor transistors formed therein, the substrate
having at least one hole for a through hole via; a pre-metal
dielectric formed over the semiconductor transistors; a hard mask
over the pre-metal dielectric; metal plugs formed through the hard
mask and the pre-metal dielectric to electrically contact the
transistors; a gapfill metal in the at least one hole, the gapfill
metal being planarized so that the metal plugs and the gapfill
metal are substantially coplanar with the top surface of the hard
mask.
2. The microelectronic device of claim 1, wherein the substrate
comprises a silicon wafer, the gapfill metal comprises copper, the
metal plugs comprise copper, and the hard mask comprises silicon
carbide or silicon carbon nitride.
3. The microelectronic device of claim 1, wherein the substrate
comprises a silicon wafer, the gapfill metal comprises copper, the
metal plugs comprise tungsten, and the hard mask comprises silicon
carbide or silicon carbon nitride.
4. The microelectronic device of claim 1, further comprising a
dielectric liner substantially surrounding the gapfill metal.
5. The microelectronic device of claim 1, further comprising a
diffusion barrier for the gapfill metal substantially surrounding
the gapfill metal.
Description
CROSS REFERENCE
[0001] The present application is a divisional of U.S. patent
application Ser. No. 12/613,518, filed Nov. 5, 2009, which is a
divisional of U.S. patent application Ser. No. 11/820,811, to Boyd
et al., filed Jun. 20, 2007, now U.S. Pat. No. 7,615,480. This
application is related to U.S. Pat. No. 7,592,259; U.S. Pat. No.
7,749,893; U.S. patent application Ser. No. 11/821,051, to Boyd et
al., filed Jun. 20, 2007; and U.S. patent application Ser. No.
11/820,810, to Boyd et al., filed Jun. 20, 2007. All of these
patents and/or applications are incorporated herein, in their
entirety, by this reference for all purposes.
BACKGROUND
[0002] This invention pertains to three dimensional integrated
circuits and methods, of fabricating three-dimensional integrated
circuits; more specifically this invention relates to methods of
post-contact back end of line through-hole via integration for
interconnect metallization for three-dimensional integrated
circuits.
[0003] A three-dimensional integrated circuit includes two or more
semiconductor chips with integrated circuits or includes two or
more semiconductor wafers with integrated circuits. The
semiconductor chips or semiconductor wafers are stacked together,
bonded, and electrically interconnected in three dimensions, i.e.,
integrated within the semiconductor chips or semiconductor wafers
and integrated between the semiconductor chips or semiconductor
wafers. The interconnections between the chips or between the
wafers are accomplished by way of through holes from the back side
to the front side of one or more of the chips or one or more of the
semiconductor wafers. In other words, the electrical connections
between the stack of chips or stack of wafers are made by way of
the through holes. Three-dimensional integrated circuits may have a
large number of through holes for interconnect metallization
between the semiconductor chips or between the semiconductor
wafers.
[0004] Three-dimensional integrated circuits, according to some
designs, will use through-hole vias that are large, high aspect
ratio features with dimensions an order of magnitude or more larger
than the minimum geometry features for standard technology dual
damascene metallization interconnects. The through hole vias may
require diameters of about 5-10 micrometers. The length for some of
the through holes may be about 25 micrometers or more.
Consequently, the aspect ratios for processing the through holes
are extremely high in comparison to standard technologies for
fabricating two-dimensional integrated circuits. Typical processes
for fabricating two-dimensional integrated circuits cannot easily
handle the large holes and extremely high aspect ratios that will
be required for fabricating three-dimensional integrated
circuits.
[0005] Furthermore, the process steps and process conditions
required for forming the through hole vias to achieve
three-dimensional integration are incompatible with many of the
standard technology front end of line (FEOL) processes and standard
back end of line (BEOL) processes used for the within wafer
two-dimensional integration for fabricating semiconductor devices.
Modifications to the standard FEOL processes and/or standard BEOL
processes can be made but at what may be unacceptably high costs
and risks. In other words, it is generally undesirable to
manufacturers of semiconductor devices to develop and implement new
processes. For some semiconductor fabrication processes, even minor
modifications to the process can incur a substantial learning
curve, which can be both time consuming and costly because of
development costs and the tremendous costs associated with testing,
process integration, and yield optimization.
[0006] Clearly, there is a need for device structures and processes
for manufacturing substrates for three-dimensional integrated
circuits that do not require extensive modifications to the
standard technologies of FEOL processing or BEOL processing. The
practical fabrication of three-dimensional integrated circuits will
require new processes that can meet the requirements for
metallization of three-dimensional integrated circuits. More
specifically, there is a need for new processes capable of meeting
the unusual aspect ratio requirements for through hole via
metallization for three-dimensional integrated circuits while
requiring little or no significant modifications to standard
technology FEOL processes and BEOL processes used for the within
wafer two-dimensional integration.
SUMMARY
[0007] This invention pertains to three-dimensional integrated
circuits and methods of fabricating three-dimensional integrated
circuits that include post-contact back end of line through-hole
via integration for three-dimensional integrated circuits. The
present invention seeks to overcome one or more of the deficiencies
in the standard technologies for fabricating three-dimensional
integrated circuits such as integrated stacks of semiconductor
chips or semiconductor wafers with integrated circuits.
[0008] One aspect of the present invention is a method of
processing substrates comprising a semiconductor for
three-dimensional integrated circuits. In one embodiment, the
method comprises forming metal plug contacts through a hard mask
and a premetal dielectric to transistors in the semiconductor. The
method also includes etching a hole for a through-hole via through
the hard mask to the semiconductor using a patterned photoresist
process, removing the patterned photoresist and using a hard mask
process to etch the hole to an amount into the semiconductor. The
method further includes depositing a dielectric liner to isolate
the hole from the semiconductor, depositing a gapfill metal to fill
the hole, and planarizing the surface of the substrate to the hard
mask.
[0009] Another embodiment of the present invention is a method of
processing substrates for three-dimensional integrated circuits.
The method comprises forming metal plug contacts through a premetal
dielectric to transistors in a semiconductor and etching a hole for
a through-hole via through the premetal dielectric to an amount
into the semiconductor. The method also includes depositing a
dielectric liner to isolate the hole from the semiconductor,
depositing a gapfill metal in the hole, and planarizing the surface
of the substrate to the dielectric liner.
[0010] Another aspect of the present invention includes
three-dimensional integrated circuits fabricated according to
methods of the present invention.
[0011] It is to be understood that the invention is not limited in
its application to the details of construction and to the
arrangements of the components set forth in the following
description or illustrated in the drawings. The invention is
capable of other embodiments and of being practiced and carried out
in various ways. In addition, it is to be understood that the
phraseology and terminology employed herein are for the purpose of
description and should not be regarded as limiting.
[0012] As such, those skilled in the art will appreciate that the
conception, upon which this disclosure is based, may readily be
utilized as a basis for the designing of other structures, methods,
and systems for carrying out aspects of the present invention. It
is important, therefore, that the claims be regarded as including
such equivalent constructions insofar as they do not depart from
the spirit and scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a process flow diagram of an embodiment of the
present invention.
[0014] FIG. 2.1 is a diagram of a substrate to be processed
according to an embodiment of the present invention.
[0015] FIG. 2.2 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0016] FIG. 2.3 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0017] FIG. 2.4 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0018] FIG. 2.5 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0019] FIG. 2.6 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0020] FIG. 2.7 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0021] FIG. 2.8 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0022] FIG. 2.9 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0023] FIG. 2.10 is a diagram of a substrate processed according to
an embodiment of the present invention.
[0024] FIG. 3 is a process flow diagram of an embodiment of the
present invention.
[0025] FIG. 4.1 is a diagram of a substrate to be processed
according to an embodiment of the present invention.
[0026] FIG. 4.2 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0027] FIG. 4.3 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0028] FIG. 4.4 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0029] FIG. 4.5 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0030] FIG. 4.6 is a diagram of a substrate partially processed
according to an embodiment of the present invention.
[0031] FIG. 4.7 is a diagram of a substrate processed according to
an embodiment of the present invention.
[0032] Skilled artisans appreciate that elements in the figures are
illustrated for simplicity and clarity and have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements in the figures may be exaggerated relative to other
elements to help to improve understanding of embodiments of the
present invention.
DESCRIPTION
[0033] The present invention pertains to interconnect metallization
for three-dimensional integrated circuits. More specifically, the
present invention pertains to a process flow for forming holes and
metal gapfill of the holes for through-hole vias for metallization
lines running through a semiconductor wafer or other substrate. The
metallization is usually used for the upper level semiconductor
device substrates used in three-dimensional integrated
circuits.
[0034] The operation of embodiments of the present invention will
be discussed below, primarily, in the context of processing
semiconductor wafers for use in stacked wafer three-dimensional
integrated circuits. More specifically, the operation of
embodiments of the present invention is discussed below in the
context of processing silicon wafers for three-dimensional silicon
integrated circuits. However, it is to be understood that
embodiments in accordance with the present invention may be used
for other semiconductor devices and other semiconductor wafers.
[0035] In the following description of the figures, identical
reference numerals have been used when designating substantially
identical elements or steps that are common to the figures.
[0036] Reference is now made to FIG. 1 where there is shown a
process flow diagram 2 according to one embodiment of the present
invention. Process flow diagram 2 shows a method of fabricating
three-dimensional integrated circuits. More specifically, process
flow diagram 2 shows substrate processing for the three-dimensional
integrated circuits. Process flow diagram 2 includes step 4, step
6, step 8, step 10, step 12, step 14, and step 16.
[0037] Step 4 includes forming metal plug contacts through a hard
mask and a premetal dielectric to electrically contact
semiconductor transistors for the three-dimensional integrated
circuits. Step 4 is performed on a substrate for a
three-dimensional integrated circuit. The semiconductor transistors
are incorporated as part of the substrate. The semiconductor
transistors can be formed by techniques known to persons of
ordinary skill in the art for forming transistors. Preferably, the
transistors are formed using standard technology for front end of
line (FEOL) processing of semiconductor devices from semiconductor
wafers or other substrates having a suitable semiconductor for
transistors.
[0038] The semiconductor wafer has a premetal dielectric applied
over the transistors and the surface of a semiconductor wafer. The
premetal dielectric can be any of the standard technology materials
for premetal dielectrics used in standard technology FEOL
processing of semiconductor transistors or other material suitable
for use as a premetal dielectric. The premetal dielectric may
comprise an electrically insulating material such as boron
phosphorus silicon glass (BPSG) or other glass with suitable
properties for a premetal dielectric.
[0039] The hard mask recited in step 4 comprises a material
suitable for use as a hard mask for lithography purposes such as
hard mask materials typically used in processing semiconductor
devices. The hard mask is disposed as a layer over the premetal
dielectric. Examples of some of the materials that can be used for
the hard mask include, but are not limited to, silicon carbide and
silicon carbon nitride.
[0040] According to a preferred embodiment of the present
invention, step 4 includes etching contact vias through the hard
mask and through the premetal dielectric. The metal plugs are
formed in the contact vias to make electrical contact with the
transistors. The metal plugs are planarized so that they are
coplanar with the surface of the hard mask.
[0041] The metal plugs may comprise standard technology metal plugs
such as tungsten plugs. As an option, the metal plugs may comprise
copper metal plugs or metal plugs of other materials suitable for
metal contacts to transistors. For copper metal plugs, the
formation of the metal plugs may include one or more additional
steps to provide a passivation coating or barrier for the
copper.
[0042] Step 6 of process flow 2 includes etching a hole to the
semiconductor using a patterned photoresist process. More
specifically, a dry etch process such as plasma etching and
reactive ion etching is performed using a patterned photoresist to
etch through the hard mask and the premetal dielectric. For some
embodiments of the present invention, additional layers of
dielectrics such as a dielectric for shallow trench isolation may
be present between the premetal dielectric and the semiconductor.
The additional dielectrics, if present, are also etched in step
6.
[0043] The patterned photoresist is lithographically patterned so
that the areas of the substrate intended for placement of the hole
are exposed for etching. The patterned photoresist etch process may
include one or more processes typically used for etching dielectric
materials such as the hard mask, the premetal dielectric, and the
dielectric for shallow trench isolation. Suitable equipment and
processes for performing the etch in step 6 are available from
companies such as Lam Research Corporation of Fremont, Calif.
[0044] Step 8 includes removing the photoresist and using the hard
mask with a hard mask process to etch the hole into the
semiconductor. The hole formed in the semiconductor is a blind
hole. Suitable equipment and processes for etching the
semiconductor are available from companies such as Lam Research
Corporation of Fremont, Calif. The hole is etched into the
semiconductor to an amount so that the hole has a depth suitable
for forming a through hole from the blind hole formed in step 8 by
removing material from the backside of the substrate during later
processing.
[0045] The dimensions of the hole formed in step 6 and step 8 are
selected based on the design requirements for the three-dimensional
integrated circuits. According to one embodiment of the present
invention, the dimensions of the hole may include diameters in the
range of 1-10 micrometers and depths of 25 micrometers to 40
micrometers, and all values, ranges, and subranges subsumed
therein. For other embodiments of the present invention, the hole
may have a diameter larger than 10 micrometers and may have a depth
greater than 40 micrometers.
[0046] Step 10 of process flow 2 includes deposition of a
dielectric liner. The dielectric liner is deposited over the
surface of the substrate and the surfaces of the hole formed in
step 6 and step 8. A variety of suitable dielectrics can be used
for the dielectric liner. Some examples of materials that can be
used for the dielectric liner include, but are not limited to,
tetraethyl ortho silicate oxide, silicon carbide, silicon carbon
nitride, carbon doped glass, aluminum oxide, and others.
[0047] Step 12 of process flow 2 includes depositing a
metallization diffusion barrier for a gapfill metal. Step 12 may
not be needed for some embodiments of the present invention. More
specifically, the metallization diffusion barrier may not be needed
if the dielectric liner deposited in step 10 is capable of
preventing diffusion of the gapfill metal. However, for a preferred
embodiment of the present invention, copper metallization is used.
Preferably, a metallization diffusion barrier suitable for use with
copper metallization is deposited in step 12. Examples of preferred
metallization diffusion barriers for copper include, but are not
limited to, tantalum, tantalum nitride, tantalum on tantalum
nitride, and ruthenium on tantalum nitride. In a preferred
embodiment of the present invention, the metallization diffusion
barrier includes ruthenium on tantalum nitride with the ruthenium
deposited by a process such as atomic layer deposition and the
tantalum nitride deposited by a process such as atomic layer
deposition.
[0048] Step 14 of process flow 2 includes depositing the gapfill
metal. As indicated above, preferred embodiments for
three-dimensional integrated circuits according to the present
invention use copper metallization. Step 14 includes depositing
copper as the gapfill metal. A variety of processes can be used for
depositing the gapfill metal. Preferred processes for depositing
copper for copper metallization include wet chemical processes such
as electrochemical plating of copper and such as electroless
deposition of copper. As an option for some embodiments of the
present invention for copper gapfill, a copper seed layer may also
be deposited prior to depositing the gapfill copper.
[0049] Step 16 of process flow 2 includes planarization of the
surface of the substrate to the hard mask. The planarization is
done to remove excess materials on the surface of the substrate
such as overburden from the gapfill metal deposition and other
layers and to uncover the metal plugs. After the planarization, the
surface of the metal plugs and the surface of the gapfill metal in
the hole are coplanar. This means that making electrical contacts
to the metal plugs and to the gapfill metal in the hole is more
easily accomplished because vias etched to make the electrical
contacts to the metal plugs and to the gapfill metal require
substantially the same amount of etching.
[0050] Additional process steps following step 16 may include steps
such as providing a passivation or barrier layer over the gapfill
metal, if needed. Further processing of the substrates include any
additional steps needed to form one or more metallization levels
using standard technologies for BEOL processing of semiconductor
devices. In general, process flow 2 allows the FEOL processes to be
carried out without major modification of standard practices for
FEOL processing. Similarly, process flow 2 allows the BEOL
processes to be carried out without major modification of standard
practices for BEOL processing. In other words, process flow 2
allows formation of structures for through hole metallization for
three-dimensional integrated circuits without substantial
modification of standard practices for FEOL and BEOL
processing.
[0051] Substrates processed according to process flow 2 will have
additional process steps to convert the metal filled blind hole
into a through hole for a metallization via. According to preferred
embodiments of the present invention, the through hole is formed by
removing material from the back side of the substrate to open the
bottom of the hole formed in step 6 and step 8. The removal of the
material from the backside of the substrate can be accomplished
using one or more or a combination of known processes such as
grinding, etching, and chemical mechanical planarization. Standard
processing practices can be used for vertical stacking and
interconnection of the substrates into three-dimensional integrated
circuits.
[0052] To further illustrate the process flow presented in FIG. 1,
reference is now made to FIG. 2.1 through FIG. 2.10 where there is
shown a cross sectional side view of a section of a device wafer
20-1 to be processed (shown in FIG. 2.1) and as being processed
(shown in FIG. 2.2 through FIG. 2.10) according to process flow 2
in FIG. 1. Device wafer 20-1 includes a substrate 22 comprising a
semiconductor having a transistor that includes source drain
regions 24 and a gate 26 as commonly used in semiconductor device
technologies. Optionally, substrate 22 may be a semiconductor wafer
such as a silicon wafer with doped areas to form source drain
regions 24. Alternatively, substrate 22 may comprise an insulating
material such as sapphire or glass supporting a layer of a
semiconductor such as silicon.
[0053] FIG. 2.2 shows a device wafer 20-2. Device wafer 20-2
includes device wafer 20-1 having a premetal dielectric 28 and a
layer of a hard mask 30. Premetal dielectric 28 may comprise an
electrically insulating material such as boron phosphorus silicon
glass (BPSG) or other glass with suitable properties for a premetal
dielectric used in FEOL processing. Hard mask 30 is disposed over
premetal dielectric 28. Examples of some of the materials that can
be used for hard mask 30 include, but are not limited to, silicon
carbide and silicon carbon nitride.
[0054] FIG. 2.3 shows a device wafer 20-3 which includes device
wafer 20-2 having contact vias 32 etched through hard mask 30 and
premetal dielectric 28 for the formation of contact plugs. Contact
vias 32 can be etched using standard technology etch processes such
as plasma etching and reactive ion etching.
[0055] FIG. 2.4 shows a device wafer 20-4 which includes a device
wafer 20-3 having metal plugs 34 contacting source drain regions 24
and gate 26. Metal plugs 34 are formed in contact vias 32 and are
planarized so that they are coplanar with the surface of hard mask
30. Metal plugs 34 may comprise standard technology metal plugs
such as tungsten plugs. As an option, the metal plugs may comprise
copper metal plugs or metal plugs of other materials suitable for
metal contacts to transistors. For copper metal plugs, the
formation of metal plugs 34 may include one or more additional
steps to provide a passivation coating or barrier over the surface
of the copper.
[0056] FIG. 2.5 shows a device wafer 20-5 which includes device
wafer 20-4 having a photoresist layer 36 applied to the surface.
FIG. 2.6 shows a device wafer 20-6 including device wafer 20-5 with
photoresist layer 36 having a patterned area 36A for etching. More
specifically, photoresist layer 36 is used with a photoresist etch
process to etch through hard mask 30 and premetal dielectric 28. If
additional layers of dielectric are present before reaching the
semiconductor, then those additional layers of dielectric can also
be etched using the photoresist etch process. Examples of some
additional dielectric layers that may need to be etched include
dielectric layers for shallow trench isolation and dielectrics for
semiconductor on insulator structures. After etching through the
dielectrics, photoresist layer 36 can be removed and a hard mask
etch process can be used to continue etching into the
semiconductor.
[0057] FIG. 2.7 shows a device wafer 20-7 which includes device
wafer 20-6 after completion of the etch processing. More
specifically, photoresist 36 has been removed and device wafer 20-7
has a hole 40 to be used for formation of a through hole via. Hole
40 has been formed by etching through hard mask 30, premetal
dielectric 28, any additional dielectric layers that may be present
in some device structures (additional dielectric layers not shown
in FIG. 2.7), and into the semiconductor. Hole 40 has been etched
to the depth desired so that hole 40 can be converted into a
through hole via during later processing steps for fabrication of
the three-dimensional integrated circuit. According to one
embodiment of the present invention, the dimensions of hole 40 may
include diameters in the range of 1-10 micrometers and depths of 25
micrometers to 40 micrometers, and all values, ranges, and
subranges subsumed therein. For other embodiments of the present
invention, the hole may have a diameter larger than 10 micrometers
and a depth greater than 40 micrometers.
[0058] FIG. 2.8 shows a device wafer 20-8 which includes device
wafer 20-7 with a dielectric liner 42 deposit over the surface of
device wafer 20-7 including hole 40. Dielectric liner 42 is
deposited so as to provide electrical isolation between the
semiconductor and the metallization to be formed in hole 40. A
variety of suitable dielectrics can be used for dielectric liner
42. Some examples of materials that can be used for dielectric
liner 42 include, but are not limited to, tetraethyl ortho silicate
oxide, silicon carbide, silicon carbon nitride, carbon doped glass,
aluminum oxide, and others.
[0059] FIG. 2.8 also shows device wafer 20-8 having a metallization
diffusion barrier 44 deposited over dielectric liner 42.
Metallization diffusion barrier 44 may not be needed for some
embodiments of the present invention. More specifically, the
metallization diffusion barrier may not be needed if dielectric
liner 42 is also capable of preventing diffusion of the gapfill
metal. This means that metallization diffusion barrier 44 may be
optional for some embodiments of the present invention. However,
for a preferred embodiment of the present invention, copper
metallization is used. Preferably, metallization diffusion barrier
44 is included so as to be suitable for use with copper
metallization. Examples of preferred metallization diffusion
barriers for copper include, but are not limited to, tantalum,
tantalum nitride, tantalum on tantalum nitride, and ruthenium on
tantalum nitride. In a preferred embodiment of the present
invention, metallization diffusion barrier 44 includes ruthenium on
tantalum nitride with the ruthenium deposited by a process such as
atomic layer deposition and the tantalum nitride deposited by a
process such as atomic layer deposition.
[0060] FIG. 2.9 shows a device wafer 20-9 which includes device
wafer 20-8 further processed to include gapfill metal 46. After
deposition of gapfill metal 46, further process steps include
planarization to the surface of hard mask 30. The planarization is
performed so as to remove overburden metal that may have been
formed during deposition of gapfill metal 46 and to remove the
portions of the barrier layer 44 and portions of dielectric liner
42 that were deposited outside of hole 40. The planarization makes
the surface of gapfill metal 46 coplanar with the surface of hard
mask 30 and metal plugs 34. For a preferred embodiment of the
present invention, gapfill metal 46 comprises copper for copper
metallization. FIG. 2.9 further shows device wafer 20-9 having a
sealing layer 48 provided so as to at least isolate gapfill metal
46 from areas of the semiconductor device that could be harmed by
contamination with gapfill metal 46, as can occur for copper
metallization. Furthermore, for embodiments of the present
invention that include using copper for metal plugs 34, sealing
layer 48 can provide isolation for metal plugs 34.
[0061] A variety of options is available for the material and
configuration for sealing layer 48. As one option, sealing layer 48
may comprise a diffusion barrier material such as, but not limited
to, silicon carbide, silicon carbon nitride, silicon nitride, and
other dielectric materials with sufficient diffusion barrier
properties. Alternatively, sealing layer 48 may comprise a barrier
layer for copper metallization such as a selectively applied layer
of cobalt tungsten boron phosphide or other material with
sufficient copper diffusion barrier properties. Embodiments of the
present invention that include sealing layer 48 selectively applied
to the metallization will not include a continuous layer for
sealing layer 48 as shown in FIG. 2.9.
[0062] FIG. 2.10 shows a device wafer 20-10 which includes device
wafer 20-9 and BEOL structure 50. BEOL structure 50 includes one or
more metallization levels formed to interconnect the transistors
and gapfill metal 46. As an option, BEOL structure 50 may be formed
using standard technology BEOL processes for multiple level
metallization for electronic devices. Further processing of
electronic devices from device wafer 20-10 may include process
steps to remove material from the backside of the substrate 22 so
as to open the bottom of hole 40 to form a through hole. Still
further processing includes stacking and interconnecting device
wafer 20-10 with another device wafer to form a three-dimensional
integrated circuit. Alternatively, two or more of device wafer
20-10 may be stacked and interconnected to form a three-dimensional
integrated circuit. As another option, two or more of device wafer
20-10 may be stacked and interconnected with another wafer to form
a three-dimensional integrated circuit.
[0063] Reference is now made to FIG. 3 where there is shown a
process flow diagram 103 according to another embodiment of the
present invention. Process flow diagram 103 shows a method of
fabricating three-dimensional integrated circuits. More
specifically, process flow diagram 103 shows substrate processing
for the three-dimensional integrated circuits. Process flow diagram
103 includes step 105, step 107, step 110, step 112, step 114, and
step 117.
[0064] Step 105 includes forming metal plug contacts through a
premetal dielectric to electrically contact semiconductor
transistors for the three-dimensional integrated circuits. Step 105
is performed on a substrate for a three-dimensional integrated
circuit. The semiconductor transistors are incorporated as part of
the substrate. The semiconductor transistors can be formed by
techniques known to persons of ordinary skill in the art for
forming transistors. Preferably, the transistors are formed using
standard technology for FEOL processing of semiconductor devices
from semiconductor wafers or other substrates having a suitable
semiconductor for transistors.
[0065] The semiconductor wafer has a premetal dielectric applied
over the transistors and the surface of a semiconductor wafer. The
premetal dielectric can be any of the standard technology materials
for premetal dielectrics used in standard technology front end of
line processing of semiconductor transistors or other material
suitable for use as a premetal dielectric. The premetal dielectric
may comprise an electrically insulating material such as boron
phosphorus silicon glass or other glass with suitable properties
for a premetal dielectric.
[0066] According to a preferred embodiment of the present
invention, step 105 includes etching contact vias through the
premetal dielectric for the metal plugs to contact the transistors.
The metal plugs are formed in the contact vias and are planarized
so that they are coplanar with the surface of the premetal
dielectric. The metal plugs may comprise standard technology metal
plugs such as tungsten plugs. As an option, the metal plugs may
comprise copper metal plugs or metal plugs of other materials
suitable for metal contacts to transistors. For copper metal plugs,
the formation of the metal plugs may include one or more additional
steps to provide a passivation coating or barrier for the
copper.
[0067] Step 107 of process flow 103 includes etching a hole to the
semiconductor using a patterned photoresist process. More
specifically, a dry etch process such as plasma etching and
reactive ion etching is performed using a patterned photoresist to
etch through the premetal dielectric and deep into the
semiconductor. For some embodiments of the present invention
additional layers of dielectrics such as a dielectric for shallow
trench isolation and a dielectric for semiconductor on insulator
structures may be present between the premetal dielectric and the
semiconductor. The additional dielectrics, if present, are also
etched in step 107.
[0068] The patterned photoresist is lithographically patterned so
that the areas of the substrate for placement of the hole are
exposed for etching. The patterned photoresist etch process may
include one or more processes typically used for etching dielectric
materials such as the premetal dielectric, the dielectric for
shallow trench isolation, the dielectric for semiconductor on
insulator structures (if present), and the semiconductor. Suitable
equipment and processes for performing the etching in step 107 are
available from companies such as Lam Research Corporation of
Fremont, Calif.
[0069] The dimensions of the hole formed in step 107 are selected
based on the design requirements for the three-dimensional
integrated circuits. According to one embodiment of the present
invention, the dimensions of the hole may include diameters in the
range of 1-10 micrometers and depths of 25 micrometers to 40
micrometers, and all values, ranges, and subranges subsumed
therein. For other embodiments of the present invention, the hole
may have a diameter larger than 10 micrometers and may have a depth
greater than 40 micrometers.
[0070] Step 110 of process flow 103 includes deposition of a
dielectric liner. The dielectric liner is deposited over the
surface of the substrate and the surfaces of the hole formed in
step 107. A variety of suitable dielectrics can be used for the
dielectric liner. Some examples of materials that can be used for
the dielectric liner include, but are not limited to, tetraethyl
ortho silicate oxide, silicon carbide, silicon carbon nitride,
aluminum oxide, carbon doped glass, and others. The dielectric
liner is deposited so as to provide electrical isolation for the
semiconductor.
[0071] Step 112 of process flow 103 includes depositing a
metallization diffusion barrier for a gapfill metal. Step 112 may
not be needed for some embodiments of the present invention. More
specifically, the metallization diffusion barrier may not be needed
if the dielectric liner deposited in step 110 is capable of
preventing diffusion of the gapfill metal. However, for a preferred
embodiment of the present invention, copper metallization is used.
Preferably, a metallization diffusion barrier suitable for use with
copper metallization is deposited in step 112. Examples of
preferred metallization diffusion barriers for copper include, but
are not limited to, tantalum, tantalum nitride, tantalum on
tantalum nitride, and ruthenium on tantalum nitride. In a preferred
embodiment of the present invention, the metallization diffusion
barrier includes ruthenium on tantalum nitride with the ruthenium
deposited by a process such as atomic layer deposition and the
tantalum nitride deposited by a process such as atomic layer
deposition.
[0072] Step 114 of process flow 103 includes depositing the gapfill
metal. As indicated above, preferred embodiments for
three-dimensional integrated circuits according to the present
invention use copper metallization. Step 114 includes depositing
copper as the gapfill metal. A variety of processes can be used for
depositing the gapfill metal. Preferred processes for depositing
copper for copper metallization include wet chemical processes such
as electrochemical plating of copper and such as electroless
deposition of copper. As an option for some embodiments of the
present invention for copper gapfill, a copper seed layer may also
be deposited prior to depositing the gapfill copper.
[0073] Step 117 of process flow 103 includes planarization of the
surface of the substrate to the dielectric liner. The planarization
is done to remove excess materials on the surface of the substrate
such as overburdened from the gapfill metal deposition and other
layers so that the only the dielectric liner remains over the metal
plugs. After the planarization, the surface of the gapfill metal is
coplanar with the surface of the dielectric liner.
[0074] Additional process steps following step 117 may include
steps such as providing a passivation or barrier layer over the
gapfill metal, if needed. Further processing of the substrates
include any additional steps needed to form one or more
metallization levels using standard technologies for BEOL
processing of semiconductor devices. In general, process flow 103
allows the FEOL processes to be carried out without major
modification of standard practices for FEOL processing. Similarly,
process flow 103 allows the BEOL processes to be carried out
without major modification of standard practices for BEOL
processing. In other words, process flow 103 allows formation of
structures for through hole metallization for three-dimensional
integrated circuits without substantial modification of standard
practices for FEOL and BEOL processing.
[0075] Substrates processed according to process flow 103 will have
additional process steps to convert the metal filled blind hole
into a through hole via for metallization. According to preferred
embodiments of the present invention, the through hole is formed by
removing material from the backside of the substrate to open the
bottom of the hole formed in step 107. The removal of the material
from the backside of the substrate maybe accomplished using one or
more or a combination of known processes such as grinding, etching,
and chemical mechanical planarization. Standard processing
practices can be used for vertical stacking and interconnection of
the substrates into three-dimensional integrated circuits.
[0076] To further illustrate the process flow presented in FIG. 3,
reference is now made to FIG. 4.1 through FIG. 4.7 where there is
shown a cross sectional side view of a section of a device wafer
being processed (shown in FIG. 4.1 through FIG. 4.7) according to
process flow 103 in FIG. 3. FIG. 4.1 shows a device wafer 120-1
having a substrate 122 comprising a semiconductor having a
transistor that includes source drain regions 124 and a gate 126 as
commonly used in semiconductor device technologies. Optionally,
substrate 122 may be a semiconductor wafer such as a silicon wafer
with doped areas to form source drain regions 124. Alternatively,
substrate 122 may comprise an insulating material such as sapphire
or glass supporting a layer of a semiconductor such as silicon.
[0077] Device wafer 120-1 includes a premetal dielectric 128.
Premetal dielectric 128 may comprise an electrically insulating
material such as boron phosphorus silicon glass or other glass with
suitable properties for a premetal dielectric used in FEOL
processing. FIG. 4.1 shows device wafer 120-1 having contact vias
etched through premetal dielectric 128. Device wafer 120-1 also
includes metal plugs 134 formed in the contact vias so as to
electrically contact source drain regions 124 and gate 126. Metal
plugs 134 are planarized so that they are coplanar with the surface
of premetal dielectric 128. Metal plugs 134 may comprise standard
technology metal plugs such as tungsten plugs. As an option, metal
plugs 134 may comprise copper metal plugs or metal plugs of other
materials suitable for electrical contacts to transistors. For
copper metal plugs, the formation of metal plugs 134 may include
one or more additional steps to provide a passivation coating or
barrier for the copper. The contact vias can be etched using
standard technology etch processes such as plasma etching and
reactive ion etching.
[0078] FIG. 4.2 shows a device wafer 120-2 which includes device
wafer 120-1 having a photoresist layer 136 applied to the surface.
FIG. 4.3 shows a device wafer 120-3 including device wafer 120-2
with photoresist layer 136 having a patterned area 136A for
etching. More specifically, photoresist layer 136 is used with a
photoresist etch process to etch through premetal dielectric 128.
If additional layers of dielectric are present before reaching the
semiconductor, then those additional layers of dielectric can also
be etched using the photoresist etch process. Examples of some
additional dielectric layers that may need to be etched include
dielectric layers for shallow trench isolation and dielectrics for
semiconductor on insulator structures.
[0079] FIG. 4.4 shows a device wafer 120-4 which includes device
wafer 120-3 after completion of the etch processing. More
specifically, photoresist 136 has been removed and device wafer
120-4 has a hole 140 to be used for formation of a through hole
via. Hole 140 has been formed by etching through premetal
dielectric 28, any additional dielectric layers that may be present
in some device structures (additional dielectric layers not shown
in FIG. 4.4) and into the semiconductor. Hole 140 has been etched
to the depth desired so that hole 140 can be converted into a
through hole via during later processing steps for fabrication of
the three-dimensional integrated circuit. According to one
embodiment of the present invention, the dimensions of hole 140 may
include diameters in the range of 1-10 micrometers and depths of 25
micrometers to 40 micrometers, and all values, ranges, and
subranges subsumed therein. For other embodiments of the present
invention, the hole may have a diameter larger than 10 micrometers
and a depth greater than 40 micrometers.
[0080] FIG. 4.5 shows a device wafer 120-5 which includes device
wafer 120-4 and a dielectric liner 142 deposited over the surface
of device wafer 120-4 including hole 140. Dielectric liner 142 is
deposited so as to provide electrical isolation between the
semiconductor and the metallization to be formed in hole 140. A
variety of suitable dielectrics can be used for dielectric liner
142. Some examples of materials that can be used for dielectric
liner 42 include, but are not limited to, tetraethyl ortho silicate
oxide, silicon carbide, silicon carbon nitride, carbon doped glass,
aluminum oxide, and others.
[0081] FIG. 4.5 also shows device wafer 120-5 having a
metallization diffusion barrier 144 deposited over dielectric liner
142. Metallization diffusion barrier 144 may not be needed for some
embodiments of the present invention. More specifically,
metallization diffusion barrier 144 may not be needed if dielectric
liner 142 is also capable of preventing diffusion of the gapfill
metal. This means that metallization diffusion barrier 144 may be
optional for some embodiments of the present invention. However,
for a preferred embodiment of the present invention, copper
metallization is used. Preferably, metallization diffusion barrier
144 is included so as to be suitable for use with copper
metallization. Examples of preferred metallization diffusion
barriers for copper include, but are not limited to, tantalum,
tantalum nitride, tantalum on tantalum nitride, and ruthenium on
tantalum nitride. In a preferred embodiment of the present
invention, metallization diffusion barrier 144 includes ruthenium
on tantalum nitride with the ruthenium deposited by a process such
as atomic layer deposition and the tantalum nitride deposited by a
process such as atomic layer deposition.
[0082] FIG. 4.6 shows a device wafer 120-6 which includes device
wafer 120-5 further processed to include a gapfill metal 146. After
deposition of gapfill metal 146, further process steps include
planarization to the surface of dielectric liner 142 disposed
outside of hole 140. The planarization is performed so as to remove
overburden metal that may have been formed during deposition of
gapfill metal 146 and to remove the portions of barrier layer 144
that were deposited outside of hole 140. The planarization makes
the surface of gapfill metal 146 coplanar with dielectric liner 142
over metal plugs 134. For a preferred embodiment of the present
invention, gapfill metal 146 comprises copper for copper
metallization. FIG. 4.6 further shows device wafer 120-6 having a
sealing layer 148 provided so as to at least isolate gapfill metal
146 from areas of the semiconductor device that could be harmed by
contamination with gapfill metal 146, as can occur for copper
metallization.
[0083] A variety of options is available for the material and
configuration for sealing layer 148. As one option, sealing layer
148 may comprise a diffusion barrier material such as, but not
limited to, silicon carbide, silicon carbon nitride, silicon
nitride, and other dielectric materials with sufficient diffusion
barrier properties. Alternatively, sealing layer 148 may comprise a
barrier layer for copper metallization such as a selectively
applied layer of cobalt tungsten boron phosphide or other material
with sufficient copper diffusion barrier properties. Embodiments of
the present invention that include sealing layer 148 selectively
applied to the metallization will not include a continuous layer
for sealing layer 148 as shown in FIG. 4.6.
[0084] FIG. 4.7 shows a device wafer 120-7 which includes device
wafer 120-6 and BEOL structure 150. BEOL structure 150 includes one
or more metallization levels formed to interconnect the transistors
and gapfill metal 146. As an option, BEOL structure 150 may be
formed using standard technology BEOL processes for multiple level
metallization for electronic devices. Further processing of
electronic devices from device wafer 120-7 may include process
steps to remove material from the backside of the substrate 122 so
as to open the bottom of hole 140 to form a through hole. Still
further processing includes stacking and interconnecting device
wafer 120-7 with another device wafer to form a three-dimensional
integrated circuit. Alternatively, two or more of device wafer
120-7 may be stacked and interconnected to form a three-dimensional
integrated circuit. As another option, two or more of device wafer
120-7 may be stacked and interconnected with another wafer to form
a three-dimensional integrated circuit.
[0085] In the foregoing specification, the invention has been
described with reference to specific embodiments. However, one of
ordinary skill in the art appreciates that various modifications
and changes can be made without departing from the scope of the
present invention as set forth in the claims below. Accordingly,
the specification and figures are to be regarded in an illustrative
rather than a restrictive sense, and all such modifications are
intended to be included within the scope of present invention.
[0086] Benefits, other advantages, and solutions to problems have
been described above with regard to specific embodiments. However,
the benefits, advantages, solutions to problems, and any element(s)
that may cause any benefit, advantage, or solution to occur or
become more pronounced are not to be construed as a critical,
required, or essential feature or element of any or all the
claims.
[0087] As used herein, the terms "comprises," "comprising,"
"includes," "including," "has," "having," "at least one of," or any
other variation thereof, are intended to cover a non-exclusive
inclusion. For example, a process, method, article, or apparatus
that comprises a list of elements is not necessarily limited only
to those elements but may include other elements not expressly
listed or inherent to such process, method, article, or apparatus.
Further, unless expressly stated to the contrary, "or" refers to an
inclusive or and not to an exclusive or. For example, a condition A
or B is satisfied by any one of the following: A is true (or
present) and B is false (or not present), A is false (or not
present) and B is true (or present), and both A and B are true (or
present).
[0088] Further, unless expressly stated to the contrary, "at least
one of" is to be interpreted to mean "one or more." For example, a
process, method, article, or apparatus that comprises one or more
of a list of elements and if one or more of the elements comprises
a sub-list of sub-elements, then the sub-elements are to be
considered in the same manner as the elements. For example, at
least one of A and B is satisfied by any one of the following: A is
true (or present) and B is false (or not present), A is false (or
not present) and B is true (or present), and both A and B are true
(or present).
* * * * *